This invention relates to reversible friction plates, friction pack assemblies, and a planetary transmission in which the friction elements may be used.
A large variety of mechanisms utilized in machinery employ friction plates and packs of such friction plates. For example, heavy-duty clutches may utilize such plates and packs thereof as may heavy-duty disc brakes. Similarly, planetary gear mechanisms as, for example, transmissions, where large torques are involved, may use such friction packs for braking the ring gears of one or more planetary gear assemblies.
In many such mechanisms, particularly transmissions where plural friction packs are used, one for each planetary gear assembly, the stationary plates of each friction pack have been secured between housing parts in any of a variety of ways and, in the usual case, dowels have been employed to locate the housing parts with respect to each other in order to achieve proper orientation of the various components. Such dowels require precision machining in order to achieve precise alignment and, as a consequence, fabrication of such mechanisms is considerably more expensive than would be the case if precision machining could be minimized or eliminated altogether.
Moreover, the stationary friction plates in a given pack will not all be identical. In the typical case, where the pack is compressed by a fluid operated piston, a stationary plate will immediately abut the piston so as to avoid relative rotation between the two. In order to provide for retraction of the piston when the same is not subject to fluid under pressure, a retraction spring will be engaged with that stationary plate to apply therethrough a retracting force to the piston. The retraction spring will typically be operative axially of the pack with the consequence that the remaining stationary plates in the pack must be relieved in some fashion to accommodate the retraction springs.
As a consequence, both inventory and manufacturing problems arise in that two different types of stationary friction plates must be maintained on hand and, of course, be manufactured differently.